A high affinity switch for cAMP in the HCN pacemaker channels.

Autor: Porro A; Department of Biosciences, University of Milan, Milano, Italy., Saponaro A; Department of Pharmacological and Biomolecular Sciences, University of Milan, Milano, Italy., Castelli R; Department of Biosciences, University of Milan, Milano, Italy., Introini B; Department of Biosciences, University of Milan, Milano, Italy., Hafez Alkotob A; Department of Biosciences, University of Milan, Milano, Italy., Ranjbari G; Department of Biosciences, University of Milan, Milano, Italy., Enke U; Institut für Physiologie II, Universitätsklinikum Jena, Jena, Germany., Kusch J; Institut für Physiologie II, Universitätsklinikum Jena, Jena, Germany., Benndorf K; Institut für Physiologie II, Universitätsklinikum Jena, Jena, Germany., Santoro B; Department of Neuroscience, Zuckerman Institute, Columbia University, New York, NY, USA., DiFrancesco D; Department of Biosciences, University of Milan, Milano, Italy., Thiel G; Department of Biology, TU-Darmstadt, Darmstadt, Germany., Moroni A; Department of Biosciences, University of Milan, Milano, Italy. anna.moroni@unimi.it.; Institute of Biophysics Milan, Consiglio Nazionale delle Ricerche, Milano, Italy. anna.moroni@unimi.it.
Jazyk: angličtina
Zdroj: Nature communications [Nat Commun] 2024 Jan 29; Vol. 15 (1), pp. 843. Date of Electronic Publication: 2024 Jan 29.
DOI: 10.1038/s41467-024-45136-y
Abstrakt: Binding of cAMP to Hyperpolarization activated cyclic nucleotide gated (HCN) channels facilitates pore opening. It is unclear why the isolated cyclic nucleotide binding domain (CNBD) displays in vitro lower affinity for cAMP than the full-length channel in patch experiments. Here we show that HCN are endowed with an affinity switch for cAMP. Alpha helices D and E, downstream of the cyclic nucleotide binding domain (CNBD), bind to and stabilize the holo CNBD in a high affinity state. These helices increase by 30-fold cAMP efficacy and affinity measured in patch clamp and ITC, respectively. We further show that helices D and E regulate affinity by interacting with helix C of the CNBD, similarly to the regulatory protein TRIP8b. Our results uncover an intramolecular mechanism whereby changes in binding affinity, rather than changes in cAMP concentration, can modulate HCN channels, adding another layer to the complex regulation of their activity.
(© 2024. The Author(s).)
Databáze: MEDLINE
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